Clean-out tees are used in horizontally and vertically disposed conduits or pipelines which may require periodic entry for testing, cleaning, or inspection purposes. Clean-out tees or access ports to pipelines are typically found in drain pipes, such as those located in the main plumbing drain pipes in residential or commercial structures. Pneumatic clean-out plug devices permit a user to utilize a clean-out tee or access port and to seal the pipeline for purposes of testing the pipeline for leakage, pressure testing, or the like.